Method for fabrication of a non-pneumatic survivable tire and wheel assembly

ABSTRACT

A non-pneumatic tire and wheel assembly is fabricated by forming inner and outer mold elements having apertures to receive casting blocks. A tread having an inner wall is prepared for casting and fill apertures are machined in a rim of a metal wheel. The tread, the outer mold element, the wheel, the inner mold element and the rubber casting blocks are assembled and an elastomer is introduced into the mold assembly through fill tubes inserted in the fill apertures of the wheel. The elastomer is allowed to cure at room temperature to form a tire body element and the rubber casting blocks and inner and outer mold elements are disassembled. A post-cure of the disassembled tire body element is accomplished at a high temperature.

REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 12/855,622 filedon Aug. 12, 2010, now U.S. Pat. No. 8,555,941, entitled NON-PNEUMATICSURVIVABLE TIRE, COVER AND FABRICATION PROCESSES having a commonassignee with the present application, the disclosure of which isincorporated herein by reference.

BACKGROUND INFORMATION

1. Field

Embodiments of the disclosure relate generally to the field ofnon-pneumatic tires and more particularly to embodiments for asurvivable non-pneumatic tire having molded construction with a flexiblespoke structure for tactical wheeled vehicle application including arecessed/protected wheel cover/mud guard and methods for fabrication ofthe wheel and cover.

2. Background

Tactical military vehicles are subject to extreme environments and thepotential for combat damage. Existing pneumatic tires in use on manyvehicles may be vulnerable to blast and fragmentation effects fromimprovised explosive devices (IED) and other explosive or penetratingthreats which render military vehicles inoperable and can leave theircrew stranded in harms way. Additionally, flexing of tire walls inpneumatic tires may create heating that may increase detectable thermalemissions. Armor shielding provides protection from small arms fire andfragments, but greatly increases vehicle weight, reduces payload,reduces mobility and maneuverability, and reduces vehicle range.Existing wheel/tire covers are mounted outboard of the pneumatic tiredue to the tire wall bulge where they are vulnerable to terrainobstacles and may be damaged or destroyed in the course of ruggedterrain operations.

Non-pneumatic tires have been introduced for improved durability andpuncture resistance on vehicles for many applications including tacticalmilitary vehicles for the ability to withstand blast effects andprojectile punctures that could disable a vehicle with pneumatic tires.Solid rubber tires provide desired puncture resistance but may be heavyand have excessive rotating inertia for many desired applications.Wheel/tire combinations created from plastic or composite matrixmaterials are entering use but may be difficult to fabricate in a mannerto be interchangeable with existing pneumatic tire and wheel systems onvehicles.

It is therefore desirable to provide non-pneumatic tire/wheelcombinations which exhibit the desired survivability capabilities. It isalso desirable to provide non-pneumatic tire/wheel combinations that areinterchangeable with existing pneumatic tire/wheel systems.

SUMMARY

Embodiments disclosed herein provide a non-pneumatic tire and wheelassembly which incorporates a tire tread and a conventional vehiclewheel with an elastomer tire body element molded for engagementintermediate the tread and wheel. The tire body element includesmultiple concentric layers with alternating spokes.

In certain embodiments the molded elastomer tire body element has anouter surface recessed from the tire tread and further incorporates abonded multilayer cover received within the recess. A mounting plate isbonded to the cover and attached to the wheel.

Fabrication of the non-pneumatic tire and wheel assembly is accomplishedby forming inner and outer mold elements with strut and aperturedimensions adapted for the desired spoke design and mating rubber castblocks to be received in the mold elements. A tread is prepared forcasting and a conventional wheel is machined with fill apertures in arim of the wheel. The tread, outer mold element, wheel, inner moldelement and rubber casting blocks are then assembled and an elastomer isintroduced into the mold assembly through fill tubes inserted in thefill apertures of the wheel. The elastomer is allowed to dry and therubber blocks and mold elements are then disassembled from thenon-pneumatic tire and wheel assembly. A high temperature cure is thenaccomplished.

For the embodiments including the cover, mating holes are machined in anouter recess of a rim of the wheel. A cover is fabricated by sequentiallayup of concentric layers and bonding of the layers. The cover is thenattached to a mounting ring and the cover and mounting ring are attachedto the wheel using fasteners received in the machined mating holes inthe wheel rim.

The features, functions, and advantages that have been discussed can beachieved independently in various embodiments of the present disclosureor may be combined in yet other embodiments further details of which canbe seen with reference to the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an embodiment of the non-pneumatic tire andwheel assembly with cover;

FIG. 2 is a front section view of the embodiment of FIG. 1;

FIG. 3 is an isometric exploded view of the elements of the embodimentof FIG. 1;

FIG. 4 is a partial side section view of the cover;

FIG. 5A is an isometric view of the inner tool for molding fabricationof the embodiment of FIG. 1;

FIG. 5B is the isometric view of FIG. 5A with the tire tread insertedover the inner tool;

FIG. 6A is a the isometric view of FIG. 5B with the convention wheelmounted in the tooling;

FIG. 6B is the isometric view of FIG. 6A with the outer tool securedover the tire tread;

FIG. 7 is a pictorial view of the assembled tooling with mold inserts;

FIG. 8 is a flow chart depicting the mold buildup and molding processfor fabrication of the embodiment of FIG. 1;

FIG. 9 is an isometric view of the molded cover; and,

FIG. 10 is a flow chart depicting the process for fabrication of themolded cover.

DETAILED DESCRIPTION

The embodiments described herein with respect to tactical vehicle useprovide a non-pneumatic tire with hollow spokes that do not block blastpressure, instead allowing the pressure wave to pass-through the tireventing the pressure and reducing likelihood of the tire being blown offthe wheel during a blast event. The exemplary urethane cast tire isresistant to small arms fire and is not compromised from minor smallarms bullet impacts. Since the tire is non-pneumatic, it does not sufferfrom air leakage if/when punctured. The urethane spokes are durable andof sufficient number and strength to provide redundant functionalityeven after punctures from bullets, nails or other small projectiles.Concentric spoke layers allow a greater number of load paths andflexibility. These redundant load paths provide greater tolerance to IEDblast protection and small arms fire. “Run flat or damaged” capabilityis inherent by eliminating the need for the tire to contain pressurizedair.

The embodiments further incorporate a cover that mounts inset to thewheel tread providing high durability since the cover does not protrudebeyond the outer profile of the tire tread reducing exposure topotentially damaging debris such as rocks and sticks during operations.Convex shape of the cover and durable material returns to original formafter buckling during compression of the tire/wheel in operation. Thecover keeps the tire spokes from filling with mud and dirt therebymaintaining wheel balance and ride smoothness. The combination of theelements in the embodiments reduces heat emissions associated withpneumatic tires by eliminating the rubber sidewalls found on pneumatictires and masking the tire/wheel with the wheel cover.

The fabrication process for the disclosed embodiments allows for ease ofmanufacture of the wheel/tire combination and design parameters such asspoke thickness/reinforcing fibers can easily be varied to match vehicleload requirements and ride flexibility. Further, the tire/wheelfabrication process uses original equipment manufacturer (OEM) rims andtherefore can be built for any wheeled vehicle, including tacticalvehicles such as HMMWV or Stryker providing design and manufacturingcost savings.

Referring to FIGS. 1, 2 and 3, the embodiment shown provides anon-pneumatic tire and wheel assembly 8 which incorporates a moldedelastomer tire body element 10 having concentric layers 12, 14, 16 withalternating spokes 18 of elastomer web extending between concentricrings 19. For the exemplary embodiments disclosed herein, urethane isemployed as the elastomer. However, depending on specific applicationrequirements for the vehicle tire similar materials with durometersranging from approximately 40 to 90 on the Shore A scale may beemployed. The tire body element 10 is engaged at an outer circumference20 by a tread 22 of vulcanized rubber or similar material having atraction lug and groove pattern comparable to conventional pneumatictires. The tread may be similar in design and construction to a treadblank employed in retreading of conventional pneumatic tires. Innercircumference 24 of the tire body element engages a conventional vehiclewheel 26 which may be constructed in conventional fashion with forged,pressed or cast steel or aluminum structure. As will be described ingreater detail subsequently, the tire body element 10 is molded in placeon the wheel providing an inner circumferential engagement protrusion 28extending into the recessed wheel external rim profile 30. Similarly, anouter circumferential engagement dome 32 is present on the outercircumference of the tire body element which engages a mating depression33 in the inner wall 34 of the tread. The inner circumferentialengagement protrusion 28 and outer circumferential engagement dome 32enhance engagement of the tire body element to the wheel and tread toprevent separation during operation. In alternative embodimentsadditional adherence features may be employed in the wheel and/or treadfor additional engagement of the molded tire body element.

The wheel incorporates a web 36 extending from rim 26 for standardengagement of a vehicle axle hub 38. The web may include ventilatingperforations 40 for brake cooling or wheel weight reduction and includesstandard lug bores 42 for attachment of the wheel to the hub. An innerbead ring 44 and outer bead ring 46 terminate the rim profile and arelief 48 associated with the outer bead ring receives spacers 49 for amounting plate 50.

A cover 52 is received on an outer surface 54 of the tire body elementand attached with mounting plate 50 with fasteners 51 through spacers49. The outer surface is inset from the tread side wall 56 placing thecover in a protected relief in the tread and tire body element to reduceexposure to potentially damaging debris such as rocks and sticks duringoperations. The cover reduces mud and dirt introduction into the tirebody element spokes 18 from the exterior of the mounted wheel therebymaintaining wheel balance and ride smoothness. Cover 52 is convex withrespect to outer surface 54 thereby providing resiliency to return tooriginal form after buckling during compression of the tire/wheel inoperation. The cover for the embodiment shown is a multilayeredconcentric composite structure. For the embodiment shown, the coverincorporates three layers 58, 60 and 62 of concentrically reduced radiifrom inner to outer layer as shown in FIG. 4. Mounting plate 50 isbonded to cover 52 for attachment to the wheel. For the embodimentshown, fasteners 51 are quick release ball lock alignment pins extendingthrough the mounting plate and into the wheel rim.

For exemplary embodiments, the elastomeric material employed for thetire body element is urethane such as PR1664D two-part, castable 100%solids, polyurethane elastomer produced by PRC-DeSoto International,Inc., CDP Division, 2817 Empire Avenue, Burbank, Calif. 91504. Materialsfor alternative embodiments may include Two Component Polyurethane CastElastomer Systems such as Tadco S Series with Shore Hardness from A70 toA99 produced by T.A. Davies Company, 19500 S Alameda St., East RanchoDominguez Calif. (having Polyether (PTMEG) Polyol Mixture and Polyetheror Polyester/MDI Quasi-Prepolymer Isocyanate) and industrial tire rubbercompounds such as natural rubber, styrene butadiene rubber, andpolybutadiene rubber. The resiliency of the tire body element isdetermined based on the urethane composition and spoke design. Webthickness of the web for the spokes in the exemplary embodiments rangesin thickness from approximately 1/16″ to ½″ depending on specificapplication. For the exemplary embodiment shown in the drawings, theradial spokes in the concentric layers are 0.375″and the concentricrings between the spokes are 0.3125″. The spokes may be varied in theadjacent concentric layers of alternative embodiments for tailoringoverall wheel/tire body element flexure during operation. In theembodiment shown, the spokes alternate for symmetrical adjacent supportof spokes in adjacent layers. Additionally, a simple rectangular ortrapezoidal design is shown for the cross section of the spokes. Inalternative embodiments a profiled cross section may be employed forperformance enhancement. Hardness (or flexibility) of the spokes 18 andconcentric rings 19 may be of constant durometer throughout theconcentric layers, or may vary by up to 50% to optimize performance forflexibility of the entire tire body element. The spoke design for theembodiment shown provides a net open area of 84% of the total surface ofthe tire body element thereby reducing the likelihood of penetration ofspokes by projectiles such as small arms fire and maximizing the blowthrough open area for blast survivability. In various embodimentsemploying differing numbers of concentric layers and spoke thickness arange of approximately 60% to 85% may provide optimum design. Thealternating symmetrical adjacent support allows fracture or destructionof a number of spokes in the wheel without a disabling performancereduction in the wheel/tire body element system. To enhance blastperformance, the solid cover may be configured to blow off thetire/wheel when subjected to blast forces. The cover may be attachedeither with pressure-sensitive fasteners (such as plastic rivets ordeformable plastic nuts) or frangible fasteners (or both).

The combination of the tire body element and cover in the embodimentsshown reduces heat emissions associated with pneumatic tires byeliminating the rubber sidewalls found on pneumatic tires and by maskingthe tire body element and wheel with the wheel cover.

Fabrication of the non-pneumatic tire and wheel assembly of theexemplary embodiments is accomplished by casting with a pour moldingprocess. As shown in FIGS. 5A and 5B, an outer mold element 70 isreceived within the tread 22. In various embodiments, outer mold element70 may extend from a flat plate 72 with the thickness of the outer moldelement corresponding to the recess depth of the tire body element outersurface 54 from the tread outer wall 56 or have an outer rim forengagement of the tread outer wall 56 for accurate depth placementwithin the tread to create a recess 55 in the tire body element outersurface 54. The outer mold element incorporates struts 74 correspondingto the spoke locations in the tire body element with apertures 76 toreceive rubber mold blocks as will be described in greater detailsubsequently. A center post 78 extends from the outer mold element forcentering and mounting wheel 26.

An inner mold element 80, shown in FIGS. 6A AND 6B, is concentricallyreceived over tread 22. The inner mold element incorporates struts 82and apertures 84 symmetrical with the outer mold element. Moldingmaterial fill tubes 86 (best seen in FIG. 7) interface with apertures 88(best seen in FIG. 6A) in wheel rim 30. For the embodiment shown, threefill tubes with three mating apertures are employed. Apertures 88 may becreated by drilling, machining or punch perforation of the conventionalsteel or aluminum wheels employed in the non-pneumatic tire and wheelassembly. Temporary seals for the fill tubes in the wheel rim aperturesmay be created using silicone on other caulking material.

As shown in FIG. 7, rubber casting blocks 90 are inserted throughapertures 84 in the inner mold element 80 to be received in thecorresponding apertures in the outer mold element 70 to complete thecasting mold. Sizing of the struts and apertures in the outer and innermold elements and the rubber casting blocks provides correspondingsizing of the spokes in the tire body element as cast. For casting, theelastomeric is introduced through the fill tubes to completely fill theinterstitial spaces between the rubber mold blocks.

The cast non-pneumatic tire and wheel assembly is then allowed to cureat room temperature and the rubber mold blocks and outer and inner moldelements are then removed. The cast non-pneumatic tire and wheelassembly is then cured at high temperature. For the exemplary PR1664DUrethane material, high temperature cure may be accomplished in 3 hoursat 212° F. or 12 hours at 180° F. or 16 hours at 160° F.

While disclosed for the embodiments herein as a pour casting process, inalternative fabrication methods injection molding of the tire bodyelement in standard split molds may be accomplished with bonding of thetread to the tire body element after cure. In other alternativeembodiments, the tread may be cast in conjunction with the tire bodyelement using tooling for pressure injection molding.

FIG. 8 demonstrates the manufacturing process for the cast non-pneumatictire and wheel assembly as described. The inner and outer mold elementsare machined or cast from aluminum or other appropriate tooling materialwith strut and aperture dimensions adapted for the desired spoke designto achieve required structural properties for service use and matingrubber cast blocks are prepared for insertion into the apertures in theinner and outer mold elements, step 800. The tread is then prepared forcasting, step 802. Tread from a commercial off the shelf (COTS) tiretread such as that employed for conventional tire retreading may beemployed. The conventional steel or aluminum wheel is also prepared,step 804, by machining the fill apertures in the rim. The tread, outermold element, wheel, inner mold element and rubber casting blocks arethen assembled for molding, step 806. The elastomer, urethane for theexemplary embodiment as previously described, is then introduced intothe mold assembly through the fill tubes, step 808. The elastomer isallowed to room temperature cure, step 810 and the tooling is thendisassembled from the non-pneumatic tire and wheel assembly 812. Anelevated temperature post-cure is then accomplished for thenon-pneumatic tire and wheel assembly, step 814, providing a completedsystem.

FIG. 9 shows the wheel cover 52 demonstrating the concentric layers 58,60 and 62 of reducing radius which provide the convex shaping of thecover. For the exemplary embodiment, no curved tooling is required. Thecuring and bonding process causes a small amount of shrinkage andincrease in surface tension in the layers, which when combined withdiffering thicknesses, causes the part to curve. In alternativeembodiments, use of curved tooling may be employed if necessary toobtain the correct shape with different materials or to change the shapeof the final part.

Fabrication of the cover is accomplished as shown in FIG. 10.Dimensional design of the concentrically reduced radius layers andmaterial selection, urethane for the embodiments described herein, aswell as design of the mounting plate for engagement with the conventionsteel or aluminum wheel rim recess and attachment design for the coverand plate to the wheel is accomplished in step 1000. Fabrication of thecover is accomplished by sequential layup of concentric layers on a caulplate or similar tool and bonding of the layers, step 1002, using heatand pressure in a bladder press. The bonded cover is then attached tothe mounting plate by bonding with adhesive in the present embodiment,step 1004. For the embodiment shown, the mounting plate is formed fromaluminum. In alternative embodiments, the mounting plate may be plasticor composite, or other material to reinforce the center section of thecover (such as imbedded fiberglass matting). The cover and mountingplate are then attached to the wheel using quick release lockingalignment pins received in machined mating holes through the spacers inthe wheel rim in the current embodiment, step 1006. The fasteners may beselected to be pressure-sensitive or frangible or both for blastperformance enhancement as previously described. Paint and/or othercoatings may be applied to the cover, step 1008, before or aftermounting.

Having now described various embodiments of the disclosure in detail asrequired by the patent statutes, those skilled in the art will recognizemodifications and substitutions to the specific embodiments disclosedherein. Such modifications are within the scope and intent of thepresent disclosure as defined in the following claims.

What is claimed is:
 1. A method for fabrication of a non-pneumatic tireand wheel assembly comprising: forming an inner and an outer moldelement having strut and aperture dimensions adapted for a desired spokedesign and mating rubber casting blocks to be received in the apertures;preparing a tread having an inner wall for casting; machining fillapertures in a rim of a metal wheel for a vehicle; assembling the tread,the outer mold element, the wheel, the inner mold element and the rubbercasting blocks to form a mold assembly; introducing an elastomer intothe mold assembly through fill tubes inserted in the fill apertures ofthe wheel; allowing the elastomer to cure at room temperature to form atire body element; disassembling the rubber casting blocks and inner andouter mold elements from tire body element; and post-curing thedisassembled the body element at a temperature of at least 160° F. toform a non-pneumatic tire and wheel assembly.
 2. The method of claim 1wherein the step of forming the inner and outer mold elements furthercomprises: concentrically receiving the inner and outer mold elementswith the tread, the outer mold element intruding into the tread tocreate a recess in an outer surface of the tire body element.
 3. Themethod of claim 2 further comprising machining mating holes in an outerrecess of the rim of the wheel.
 4. The method of claim 3 furtherincluding fabrication of a cover comprising the steps of: sequentiallayup of concentrically reduced radius layers, and, bonding of thelayers.
 5. The method of claim 4 further comprising attaching the coverto a mounting plate.
 6. The method of claim 5 further comprisingselecting pressure-sensitive fasteners.
 7. The method of claim 6 whereinthe step of selecting pressure-sensitive fasteners comprises selectingfasteners from a set of plastic rivets or deformable plastic nuts. 8.The method of claim 6 further comprising attaching the cover and themounting plate to the wheel using the pressure-sensitive fastenersreceived in the machined mating holes in the outer recess of the rim ofthe wheel.
 9. The method of claim 5 further comprising selectingfrangible fasteners.
 10. The method of claim 9 further comprising:receiving the cover in the recess in the outer surface of the tire bodyelement; and, attaching the cover and the mounting plate to the wheelusing the frangible fasteners received in machined mating holes in anouter recess of the rim of the wheel.
 11. The method of claim 5 furthercomprising inserting spacers in a recess in the rim of the wheel. 12.The method of claim 1 wherein the step of introducing an elastomerincludes selecting an elastomer having a durometer ranging fromapproximately 40 to 90 on the Shore A scale.
 13. The method of claim 12wherein the step of selecting an elastomer comprises selecting anelastomer from the set of urethane , Two Component Polyurethane CastElastomer Systems having Polyether (PTMEG) Polyol Mixture and Polyetheror Polyester/MDI Quasi-Prepolymer Isocyanate, natural rubber, styrenebutadiene rubber, and polybutadiene rubber.
 14. The method of claim 1wherein the step of introducing an elastomer includes forming anengagement dome on the outer circumference of the tire body elementengaging a mating depression in the inner wall of the tread.
 15. Amethod for fabrication of a blast resistant non-pneumatic tire and wheelassembly comprising: forming an inner and an outer mold element havingstrut and aperture dimensions adapted for a desired spoke design andmating rubber casting blocks to be received in the apertures; preparinga tread having an inner wall for casting; machining fill apertures in arim of a metal wheel for a vehicle; assembling the tread, the outer moldelement, the wheel, the inner mold element and the rubber castingblocks, concentrically receiving the inner and outer mold elements withthe tread, the outer mold element intruding into the tread to create arecess in an outer surface of a tire body element; introducing anelastomer into the mold assembly through fill tubes inserted in the fillapertures of the wheel; allowing the elastomer to cure at a roomtemperature to form the tire body element; disassembling the rubbercasting blocks and the inner and outer mold elements from the tire bodyelement; post-curing the disassembled tire body element at a temperatureof at least 160° F. to form a non-pneumatic tire and wheel assembly;fabricating a cover; attaching the cover to a mounting plate; andattaching the mounting plate to the metal wheel with the cover receivedin the recess in the outer surface of the tire body element.
 16. Themethod as defined in claim 15 wherein the step of attaching the mountingplate further comprises: machining mating holes in an outer relief ofthe rim of the wheel; and, attaching the cover and mounting plate to thewheel using fasteners received in the machined mating holes.
 17. Themethod of claim 16 further comprising selecting the fasteners from thegroup consisting of frangible fasteners, plastic rivets or deformableplastic nuts.
 18. The method of claim 15 wherein the step of fabricatinga cover comprises: sequentially laying up concentrically reduced radiuslayers, and, bonding the layers.
 19. The method of claim 15 wherein thestep of introducing an elastomer includes forming an engagement dome onthe outer circumference of the tire body element engaging a matingdepression in the inner wall of the tread.
 20. The method of claim 15further comprising selecting an elastomer from the set of urethane, TwoComponent Polyurethane Cast Elastomer Systems having Polyether (PTMEG)Polyol Mixture and Polyether or Polyester/MDI Quasi-PrepolymerIsocyanate, natural rubber, styrene butadiene rubber, and polybutadienerubber.